Anatomical variations of the palmaris longus muscle including its relation to the median nerve – a proposal for a new classification

Background

The palmaris longus (PL) muscle is characterised by high morphological diversity, and its tendon crosses the median nerve (MN) at different levels. Due to the fact that the palmaris longus tendon is routinely harvested for reconstruction of other tendons, knowledge of its morphological variations is clinically important. Therefore, the purpose of the study was to suggest a new morphological classification of the PL muscle and characterise the relationship of its tendon to the median nerve.

Methods

Standard dissection was performed on 80 randomised and isolated upper limbs (40 left and 40 right) fixed in a 10% formalin solution. Measurements of muscle belly and tendon were obtained. The course and location of tendon insertion, as well as its relationship to the median nerve, were noted.

Results

The palmaris longus muscle was present in 92.5% of specimens. Three types of palmaris longus muscle were identified based on the morphology of its insertion (types I-III) and these were further subdivided into three subgroups (A-C) according to the ratio of the length of the muscle belly and its tendon. The most frequent was type I (78.8%), where the tendon attached to the palmar aponeurosis, and subtype B, where the tendon-to-belly ratio was 1–1.5 (41.1%). The mean distance from the interstyloid line to the crossing between the median nerve and the palmaris longus tendon was 31.6 mm. In addition, two types of palmaris longus were described.

Conclusion

The presented classification of palmaris longus muscle types allows a better characterization of its diversity and may be useful in planning tendon grafting.

     

Fibularis Tertius: Anatomical Study and Review of the Literature

Although there is much morphological variation in the anterior compartment of the leg, there is little information about the morphological variability of the fibularis tertius muscle (FTM). The main aim of the present study was to characterize the morphology (origin and insertion) and frequency of occurrence of the FTM and to use these findings as the basis for a new classification of the fibularis tertius tendon. Classical anatomical dissection was performed on 106 lower limbs fixed in 10% formalin. The presence of the FTM and the morphology of both its origin and its insertion were described. The FTM was present in 91 limbs (85.8%). Three types of origin were observed: Type 1, the most common type, with its origin on the distal half fibula (67%); Type 2, with the origin on the distal third fibula (22%); and Type 3, with an origin from the tendon of the extensor digitorum longus (11%). In addition, six types of insertion were distinguished. The most common was Type I (45%), a single distal attachment where the tendon inserts into the shaft of the fifth metatarsal bone. The rarest was Type VI, characterized by fusion with an additional band of the fibularis brevis tendon, which gives rise to the fourth interosseus dorsalis muscle. Two morphological variants of insertion could be distinguished, fan‐shaped and band‐shaped. Both the origin and insertion of the FTM are very morphologically variable, with three types of origin (Types 1–3) and six types of insertion point (Types I–VI) observed. Knowledge of such variations is essential for both clinicians and anatomists. Clin. Anat. 32:1082–1093, 2019. © 2019 Wiley Periodicals, Inc.     

Ligaments stabilizing the sacrum and sacroiliac joint: a comprehensive review

The sacroiliac joint is a diarthrodial synovial joint in the pelvis. Anatomically, it is described as a symphysis, its synovial joint characteristics being limited to the distal cartilaginous portion on the iliac side. It is a continuous ligamentous stocking comprising interconnecting ligamentous structures and surrounding fascia. Its ligaments, the primary source of its stability, include the anterior, interosseous and dorsal sacroiliac, the iliolumbar, sacrotuberous, and sacrospinous. Structural reinforcement is also provided by neighboring fascia and muscles. Lower back pain is a common presentation of sacroiliac joint disease, the best-established treatments being corticosteroid injections, bipolar radiofrequency ablation, and sacroiliac joint fusion.

     

A proposal for a new classification for the tendon of insertion of tibialis posterior

Although the tendon of the tibialis posterior muscle (TPM) is high morphological variability, its insertion is not well defined in anatomy discussions. The aim of the work is to systematize the classification of tibialis posterior tendon insertion by anatomical dissection. Classical anatomical dissection was performed on 80 lower limbs (40 female, 40 male) fixed in 10% formalin solution. The morphology of the insertion of the tendon was evaluated, and the muscle was subjected to appropriate morphometric measurements. Four types of insertion were observed, the most common being Type III (35 cases – 43.75%): a triple distal attachment where the main tendon inserts to the navicular bone and the medial cuneiform bone, and two accessory bands insert to the medial, lateral, or intermediate cuneiform bone or to the metatarsal bones (II, III, IV, V) depending on subtypes (A–C). The second most common type was Type II (18 cases: 22.5%): a double distal attachment. Type IV (14 cases: 17.5%) was characterized by quadruple distal attachment and was also divided into three subtypes (A–B). The rarest type was Type I (13 cases: 16.25%), which was characterized by a single band: the main tendon inserts to the navicular bone and the medial cuneiform bone. The tendon of the TPM presents high morphological variability. Knowledge of the four particular types of insertions is essential for both clinicians and anatomists. Clin. Anat. 32:557–565, 2019. © 2019 Wiley Periodicals, Inc.     

Anatomical variations of the pronator teres muscle in a Central European population and its clinical significance

The pronator teres (PT) muscle is a forearm flexor with radial and ulnar heads. It is innervated by the median nerve (MN), which passes between these heads. Nerve entrapment, known as “PT syndrome”, may occur in this passage. Anatomical variations in this region may be potential risk factors of this pathology. Therefore, the aim of the study was to determine the relationship between morphologic variations of the PT and the MN. In 50 isolated, formalin-fixed upper limbs, the cubital region and the forearm were dissected. The following measurements were taken: origin of the PT muscle heads, the length of these heads, the length of the forearm, diameter of the MN and the number of its muscular branches to the pronator teres muscle. The forearms with the humeral head originating from the medial humeral epicondyle and medial intermuscular septum (72%) were significantly shorter (p = 0.0088) than those where the humeral head originated only from the medial humeral epicondyle. Moreover, in these specimens, the MN was significantly thinner (p = 0.003). The ulnar head was present in 43 limbs (86%). The MN passed between the heads of the PT muscle (74%) or under the muscle (26%). In the majority of cases, it provided two motor branches (66%). There is an association between the morphologic variation of the PT muscle heads and the course and branching pattern of the MN. Both are related to differences in forearm length. This may have an impact on the risk of PT syndrome and the performance of MN electrostimulation.     

C6 and not C5 nerve fibers more commonly contribute most to deltoid muscle innervation: anatomical study with application to better diagnosing cervical nerve injuries

Neurosurgical Review - Most anatomical textbooks list both the C5 and C6 spinal nerves as contributing to the deltoid muscle’s innervation via the axillary nerve. To our knowledge, no...